Transmitter keying system



u y 1940- F. D. ANDREWS 2,207,571

TRANSMITTER KEYING SYSTEM Filed Sept. 15, 1958 Inventor Paul D. Andrews,

H is Attorney.

- Patented J ly.

UNITEDESTATE-ST azou'u PA ENT"lorries-ff TRANSMITTER xnrmc stem! I Paulnrnndrews, Schenectady, N. rte-amm- General Electric Companm'acorporation of r New York pp i n S p m 13,1938, Serial N6; 229,730 I P:c ams.- (c1. lacce 2' My invention relates .to"keying systems for radiotransmitters or the=1ike,- and particularly to keying systems for'transmitters wherein-a space discharge device or tube is employed" as"a-keying, tube connected in series with the output circuit-of a secondspace discharge .device such as an amplifier.

It is an. object of the present invention. to provide an improved keyingsystem requiring only a small number of .parts'to beadded to existingtransmitter structures.

It is a further object to utilize, in, providing:

a keying system for, a transmitter, potential sources already present inthe transmitter, such as rectiflers for supplyingamplifier anodepotential "and grid-bias potential, as a potential source for theoperation of the keying system.

' It is a particular objectfto provide improved means forobtaining inany desired circuit, such as a circuit including a keying tube, apotential which may 'be readily changed with respect to a potentialreference point or to ground, for example from a negative to a positivepotential. I The novel features which are considered .to

be characteristic of my invention are set forth with particularity inthe appended claims. My invention itself, however, both as to itsorganivzation and method ofoperation together with further objects andadvantages thereof may best be understood by reference to thefollowingide scription taken in connection with theaccom panying drawingthe single figure whereof i1- lustrates diagrammatically at'ransmittersystem' embodying my invention. 1

In the single figure of the drawing the numeral I designates a spacedischarge device having a cathode 2, an anode 3, and control electrode4, and which-in the present embodiment'of the invention is anintermediate power amplifier of a radio transmitter. Any suitable means(not shown) may be employed to-neutralize feedback of energy between theanode and control elec trode circuits; The input and output circuits ofv the amplifier are connected-"respectively to means (not shown) forproducing, desired signals to be modulated by a keying means andforradiating the modulated signals. As, these signal producing andradiating means form no partof the present invention they will not bedescribed further herein. j

Potential for the anode-cathode circuit of discharge device I isprovidedby a. rectifier apparatusi having a potentiometer resistor 6 c'onnectedacross itsloutput circuit .1 the low' potential; ornegative end 8 'ofwhich is-at ground.

sliding contact 26'.

' The anode S ot; device I .is connected to a point of resistor 8 ofsuitable potential through a lead 9. Bias potential for the control electrod e-" cathodecircuit of device I is slmilarlyprovided by a rectifierapparatus I Iihavirrg a potentiom eter resistor II connectedacross itsoutput circuit I2 the end I3 (if-which having the higher,

or pbsitive, potential is at ground. 'The control electrode of device Iis-connected to -apoint of resistorgll' of desired potential through alead I4. I

To provide in series with the anode-cathode circuit of dischargedevice Ian impedance which 'm'ay be varied-bye. keying 'meansto be describedhereinafter, a space discharge device I5, or keying;tube, having ananode, I8, a cathode I1 and a control electrode I8 is connected betweenthe nected, preferably .adjustablyas by a slidingcon- ..tact 2| .orother suitablemeans, to a point of "anydesired potential of resistor fi,and the other terminal 22 of which is,similarly,'preferably adjustablyconnected as by a sliding contact-23 to a point of any desired potentialof resistor I I. The controlelectrode-cathode circuit of dischargedevice I5 is 'connected'to the resistor I9, the control electrode I8being adapted to be connected to any desired point of "resistor I9,preferably adjustably, by a 'means such as a sliding contact 24. Tovarythe bias potential impressed onelectrode- I8 in accordance with akeying code a keying device 25 is interposed between ground and resistorIS, the device 25 being adapted mm preferably connected adjustably tothe latter resistorb'y eans, for. example,'of a The anode potentialsupply source, comprising rectifier 5 shunted bypotentiometer resistor6, and the bias .potential'supply source, comprising I rectifier ,IOshunted. by-potentiom'eter resistor II, together constitute for theresistor I9-a single source of potential, thetwo sections of thesinglesource being connected respectively to the opposite terminals 20 and 22of resistor I9. The potential range thus provided-for resistor I9'exten'ds from' a point ofgreatest positive .po-

tential, which is terminal 21 of the first section, to an intermediate,or section, connection point indicated by numerals 8 or l3, which arerespectively the points of lowest and highest potential of the first andsecond sections, and from this intermediate point to a point of greatestnegative potential which is terminal 28 of the sec and section. In thepresent embodiment the intermediate point is at ground. Suitable filtermeans (not shown) for the out put circuits of rectiflers 5 and II! arepreferably provided which may comprise, for example, usual choke coilsin series in the output circuits and capacitors in shunt with thepotentiometers.

Since terminal 28 of resistor I9 is connected to the resistor 6 which isat positive potential and terminal 22 is connected to the resistor IIwhich is at negative potential, therefore at some point between thepositive terminal 28 and the negative terminal 22 of resistor I9 thepotential is the same as the potential of the intermediate or groundpoint, indicated by 8 or I8. The position of this floating ground" pointon resistor I9 is determined in accordance with the adjustment of thepoints of connection of terminals 20 and 22, of resistor I9, along thepotentiometer resistors Sand II. The arrangement of the single potentialsource and resistor I9 is thus such that for any given setting of theadjustment means 2 I and 23 four resistances comprised in the resistors8, II and I8 are in a Wheatstone bridge circuit. The four resistancearms of the bridge are respectively 11 between positive p0 tential.point 2I of resistor 6 and ground, 1': be-' tween ground and negativepotential point 28 of resistor II, 1': between positive potential point2| and the floating ground point of resistor I9 indicated for theillustrated particular adjustment by the numeral 29, and 11 between theassumed floating ground point 28 and negative potential point 23 ofresistor II.

Any point of resistor I8 between the positive end 28 thereof and thefloating ground" point, or point of equalpotential with that of theconnection point between the two sections of the single source, is at apotential positive with respect to the connection point (B or I8)' ofthe sections and any point of resistor I8 between the negative end 22thereof and the floating ground .point is at a potential negative withrespect to the section connection point. If, however, a conductiveconnection is made between the section connection point (8 or I3) and apoint of resistor I9 other than the floating ground point, the potentialof all points of resistor IS with respect to the section connectiondescribed embodying my invention, anode potential and bias potential areimpressed on the anode 3 and control electrode 4 respectively ofdischarge device or amplifier tube I from the rectifiers 5 and III, andthe input circuit of the discharge device I is energized by signalpotential. The control electrode circuit of the keying tube I8. isconnected to the resistor I8 in such manner, as illustrated at point 24,that when key 28 is in its illustrated open position the potential ofthe control electrode II of the tube I8 is negative with respect to thegrounded, intermediate, or connection, point (8 or I8),and to thegrounded cathode I I of this tube. Therefore, during the open conditionof key 25 the keying tube I8 interposes a high impedance in series withthe anode-cathode circuit of amplifier tube I suflicient to block thelatter tube and to prevent the transmission of the signal to theantenna. Further, the key 28 is connected, as illustrated, to-

such point 28 of resistor I8 with respect to the connection point 24 0,!control electrode I8 that when the key is in closed position, therebyconnecting the key connection point 26 of resistor I8 to the groundedintermediate or section connection point (8 or I3), the negative biaspotential impressed on electrode I8 is removed and the bias potentialbecomes positive with respect to cathode I! of keying tube I5.Therefore, under the closed condition of key 25 the keying tube becomesconducting, thereby interposing only a lower negligible impedance inseries with the anode-cathode circuit of amplifier tube I, whichaccordingly transmits the signal to.the antenna, j

or following amplifier tube, as the case may be;

Keying of the transmitter is, therefore, accomplished by alternatelyopening and closing the ground connection 28 of resistor I8 by means ofthe key 25.

My invention has been described herein in a particular embodiment forpurposes of illustration. It is to be understood, however, that theinvention is susceptible of various changes and modifications and thatby the appended claims I intend to cover any such modifications as fallwithin the true spirit and scope of my invention.

What I claim' as new and desire to secure by Letters Patent of theUnited States is:

1. In combination, a space discharge device having a cathode and acontrol electrode, a potential source, a resistance connected across twopoints of diflerent potential of said source; means to connect saidcathode to a point of said source having a potential intermediate thepotentials .of said two points, means to connect said control electrodeto a predetermined point of said resistance, and means subsequently toconnect said point of intermediate potential to a point of saidresistance which is initially of different potential from that of saidpoint of intermediate potential thereby to vary the potential of saidpredetermined point with reference to the potential of said point ofintermediate potential.

2. In combination, a space discharge device having a cathode and acontrol electrode, a source of potential, a resistance connected acrosstwo points of different potential of said source, means to connect saidcathode to a point of said source having a potential intermediate thepotentials of said two points, means to connect said control electrodeto a point of said resistance which is initially of lower potential thanthat of said point of intermediate'potential and means subsequently toconnect said point of intermediate potential to a point of saidresistance which is initially of lower potential than that of said pointof connection of said control electrode to said resistance thereby torender the potential of said last-named point of said resistancepositive with reference to the potential of said point of intermediatepotential.

3. In combination, a space discharge device having a cathode and acontrol electrode, a source of potential, a resistance connected acrosspoints of said source which are respectively of higher and lowerpotential than an intermediate point of said source, means to connectsaid cathode to said intermediate point means to connect said controlelectrode-to a point of .said resistance which is initially at a lowerpotential than that of said intermediate point whereby a potentialnegative with respect to said intermediate point is impressed on saidcontrol electrode, and means subsequently to connect said intermediatepoint to a point of said resistance which is at least as close to thepoint of lowest potential of said resistance as said point "ofconnection of said control electrode to said resistance whereby saidnegative potential is removed electrode.

4. In combination, a space discharge device having a cathode and acontrol electrode, a potential source having two sections, means toconnect said cathode to the high potential end of,

one of said sections and to the low potential end of the other section,a resistanceconnected between a point of predetermined potential of oneof said sections and a point of predetermined potential of the other ofsaid sections, means to connect said control electrode to apredetermined point of said resistance whereby a predetermined initialpotential is impressed on said control electrode, and means subsequentlyto connect said cathode to a point of said resistance which is initiallyof difierent potential from that of said cathode whereby the potentialimpressed on said ll control electrode is changed.

connect the opposite terminals of said resistance respectively to saidanode potential source and said bias potential source at points thereofrespectively of higher and lower potential than that of the point oiconnection of said cathode of said second discharge device to saidsources, means to connect said control electrode to a predeterminedpoint of said resistance whereby an initial bias voltage is impressed onsaid control electrode, and means to connect a predetermined point ofsaid resistance to said point of connection of said cathode of saidsecond discharge device to said from said control control electrode.

sources whereby abias voltage different from said initial bias voltageis impressed on said control electrode.

6. In combination, a space discharge device, a source of anodepotential'and a source of bias potential for said device, tworesistances connected respectively across said potential sources, asecond space discharge device having its anodecathode circuit connectedin series with the anode-cathode circuit of said first-named dischargedevice and said anode potential source, said second discharge devicehaving a control electrode, a keying device, means to connect thecathode of said second discharge device to the low potential end of theanode potential resistance and to the high potential end of the biaspotential resistance, a third resistance connected at the respectiveends thereof to predetermined points of said first and second-namedresistances, means to connect said control electrode to a predeterminedpoint of said last-named resistance whereby a predetermined initial biasvoltage is impressed on said control electrode, and means including saidkeying device subsequently to connect a predetermined point of saidlast-named resistance to said low potential end of said anode potentialresistance, said high potential end of said bias potential resistance,and said cathode of said second discharge device whereby a'bias voltagedifferent from said initial bias voltage is impressed on said controlelectrode.

7. In combination, a space discharge device, sources respectively ofanode potential and bias potential forsaid device, two resistancesconnected respectively across said sources, a second space dischargedevice connected in series with. the anode-cathode circuit of saidfirst-named disharge device and said anode potential source and having acathode and a control electrode. means to ground said cathode, means toground the low-potential end of theresistance connected across said.anode potential source. means to.

ground, the high-potential end of the resistance connected acrosssaidxbias potential source, a

third resistance connected at the respective ends electrode, and meanssubsequently to ground a point of-said third resistance which is atleast as close as said last-named point to the lowpotential end of saidthird resistance whereby saidnegative bias potential is removed'fromsaid PAUL n. mnnnws.

